How this calculator works
Ponderal index divides mass by the cube of length. Neonatal publications often use 100 times grams divided by centimetres cubed; this is one tenth of the kg/m³ numerical value. Select the convention before entering a known index. No newborn growth category is assigned because gestational age and the reference population matter. The result is an estimate for information only and is not medical advice.
Formula
Adult PI = Wkg/Hm³. Neonatal PI = 100 Wg/Lcm³ = 0.1 Wkg/Lm³. Rearranging gives weight = PI x H³/factor and height = cube root(factor x weight/PI).
Worked example
An adult 2.0 m tall weighing 100 kg has PI 12.5 kg/m³. A newborn weighing 3.5 kg and measuring 50 cm has neonatal PI 2.8.
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Frequently asked questions
Why are infant numbers much smaller?
They use different mass and length units and an extra factor of 100, giving one tenth of the kg/m³ value.
Is this the same as BMI?
No. BMI uses height squared; ponderal index uses height cubed.
Can the result diagnose growth restriction?
No. Newborn assessment requires gestational age, clinical measurements and an appropriate growth reference.